A SiO2-added CoPtCr magnetic layer was employed in perpendicular recording media. The microstructure, magnetic properties, and recording performance of these media are discussed. The addition of SiO2 to CoPtCr is very effective for enhancing a well-isolated fine grain structure without disturbing the epitaxial growth of CoPtCr grains on a Ru underlayer. Very fine grains with a size of ∼7 nm, are realized, surrounded by grain boundaries which consist mainly of silicon oxide. The media show a large perpendicular anisotropy Ku of ∼3.6 ×106 erg/cm3 and a KuV/kT value of more than 80, even at a CoPtCr-SiO2 thickness of 12nm, resulting in a high coercivity Hc of 4.3 kOe and high squareness Mr/Ms of 0.9. The CoPtCr-SiO2 medium has a very small signal decay of 0.4%/decade at this thickness, and exhibits excellent SNR performance together with high thermal stability at very low thickness, indicating a great potential for use in high-density perpendicular recording media.